Nuking Your Git Repo

When working with git, it’s desirable sometimes to clear all of your changes and begin working at the last commit by taking the nuclear option of deleting and re-cloning your repo.

There is an easier way to do this, however…

> git nuke master

Place this alias in your gitconfig:

# Has the same effect as deleting the entire repo and re-cloning
# Except it doesn't delete files in the .gitignore, to be safe
nuke = "!sh -c \"git checkout $1 && git stash -u && git fetch --all && git reset --hard origin/$1  && git clean -df && git submodule update --init --recursive\" -"

Usage:

git nuke branch-name

For example:

git nuke master

Breakdown

Shell commands as git aliases

First, here is the syntax for running shell commands with parameters via git aliases:

"!sh -c \"git command $1\" -"

Note: the inner quotations must be escaped with backslashes.

To run a shell command through a git alias, put an exclamation point before the command name.

From the gitconfig manual:

If the alias expansion is prefixed with an exclamation point, it will be treated as a shell command.

In the nuke alias we use this to our advantage by running sh -c the command will be given as a string, and the hyphen at the end will send it to standard input.

The symbol $1 is interpreted as the first parameter passed in, and likewise later parameters are handled by their position prefixed by a dollar sign. (First parameter: $1, Second parameter: $2, etc.)

Now that we can run shell commands with parameters from git aliases we can string together a chain of useful git commands.

> git nuke master

First, we want to checkout the branch that was passed in as a parameter:

git checkout $1 

Then we want to save local modifications away and revert the working directory to match the HEAD commit, including untracked files with the -u switch:

git stash -u

Next, we want to get all current upstream refs (this also conveniently allows us to know about all current upstream branches):

git fetch --all

Next, we want to throw away all of our uncommitted changes and reset our git repo to the latest commit of the branch we specified:

git reset --hard origin/$1

Next, we want to discard the stashed changes from before, forcing deletion of the stash with the -f flag and allowing deletion of directories that were stashed with the -d flag:

git clean -df

Finally, we ensure that our git submodules are up to date with the current branch:

git submodule update --init --recursive

Your git repo’s local branch is now completely synced with the upstream branch and your build files have been preserved.